Asked this week about his ambivalence towards a second Brexit referendum, John Swinney gave a noteworthy reply: “There are some democratic principles at stake here. People have voted in a referendum.”

He is right. Demanding a second referendum to overturn the first is high-risk in terms of democratic principles. It begs questions of how the first-time “winners” would react and why not a third if the first two have created a 1-1 draw?

Unless it is built into the rules in advance, a second referendum should not be carelessly demanded in retrospect.

So it is not caution which was remarkable but its source. Every waking hour for four years, Swinney and co have manoeuvred to create a rationale for ignoring exactly the same “democratic principle” in relation to Scotland’s constitutional position.One might expect them to be cheer-leaders for a second Brexit poll because of the precedent it would set. There are two reasons they are not . First, a “no deal Brexit” offers a degree of chaos and disillusionment best suited to their objectives.

The second is more subtle. Voting again on Brexit would not only be a second referendum but, in effect, a recall one based on outcomes which have flowed from the original result. That would affirm a less welcome precedent.

If anything has become crystal clear, it is the folly of “winner-take-all” referendums on major constitutional issues. They provided the ideal playgrounds for cynics – Salmond or Farage, Sturgeon or Rees-Mogg – who were permitted to assume (a) they only had to win once and (b) the end justified the means.

President Emmanuel Macron made this point in refreshingly plain terms when he said: “Those who said you can easily do without Europe, that it will all go very well, that it is easy and there will be lots of money, are liars”.

For Europe read UK and the same applies. If anything, our own experience was worse because the Scottish farrago of calculated untruth was dignified with the status of a White Paper, funded by taxpayers for the purpose of their own deception.

Since then, we have learned from Brexit that not only seceders will assert rights but those from whom they intend to secede. It is the end result that matters – not the fraudulent prospectus.

I have been sceptical about a second Brexit referendum in deference to the “democratic principle”. If, however, the alternative is a “no deal Brexit”, I would feel entitled to reconsider since that is so different from what was voted for in 2016.

Labour seems to be edging towards this position, having rightly given the Government time to come up with some workable settlement which respected the referendum vote. That remains the most rational outcome but if it cannot be delivered, as this week’s events tend to suggest, then all bets are off.

Jeremy Corbyn said he does not want a second Scottish referendum but would not rule out agreeing to one. There was nothing wrong with that. If there is a pro-independence majority after Holyrood elections in 2021, which I hope there won’t be, whoever is Prime Minister will face the question.

The more useful response would be to start thinking about the checks and balances which must in future surround such an event if it arises. In 2014, opposition to independence led its supporters by 10.6 per cent. Many more Scots voted to stay in the UK than, two years later, opted to stay in the EU.

None of this deterred Swinney and his associates from treating the outcome as any more than a temporary inconvenience, far less accepting it for the promised generation. Nor would it stop them in future. Democratic principles…?

The dream to which they cling is winning by a single vote on a chosen day on the basis of whatever prospectus their necessity demands – exactly the same as with Brexiteers. Failing to challenge these assumptions only encourages dishonesty and grievance-seeking in pursuit of a single objective.

Brexit confirms that referendums without safeguards which test the consequences of major constitutional change against glib prior assurances are simply an invitation to deceive. There is more to “democratic principles” than that.